1. Field of the Invention
The present invention relates to bar-code reader for reading bar codes and optical marks and a POS system employing the bar-code reader.
2. Description of the Related Art
A POS terminal is connected to a bar-code reader to read a bar code on a piece of merchandise. The bar-code reader has an optical reader for reading a bar code and a recognition unit for recognizing the bar code. The optical reader emits a laser beam, according to a predetermined scanning patterns to scan a bar code at a high speed, detects the light reflected from the bar code, and reads the bar code according to the reflected light.
The optical reader has a laser unit for emitting a laser beam, a rotating polygon mirror for reflecting the laser beam, a pattern mirror for reflecting the deflected laser beam according to a predetermined scanning pattern, a window for passing the reflected laser beam to the outside, and a photosensor for detecting the light reflected from a bar code.
The reflected light is guided by the pattern mirror and polygon mirror opposite to the emitted laser beam and is condensed by a condensing lens onto the photosensor. The photosensor provides an electric signal in proportion to the intensity of the condensed light. The output of the photosensor changes in response to the pattern of the bar code. The recognition unit processes the electric signal, to decode the bar code. The decoded data is supplied to the POS terminal connected to the bar-code reader.
According to the prior art, the laser unit, polygon mirror, pattern mirror, condensing lens, and photosensor are separately fixed to a casing of the bar-code reader.
To correctly scan a bar code, a laser beam of the laser unit must hit a predetermined position on the polygon mirror. To condense reflected light from the bar code onto the photosensor through the pattern mirror, polygon, mirrors and condensing lens, the condensing lens must be correctly positioned with respect to the polygon mirror, the distance between the condensing lens and the photosensor must be accurately set, and the optical axis of the condensing lens must be aligned with the photosensor.
If these components are incorrectly positioned, the bar-code reader may produce a read error. These components, therefore, must be carefully installed in the bar-code reader by a skilled person.
A laser source in the laser unit has a certain service life, and therefore, the laser unit must be periodically replaced. This replacement must also be made carefully.
The laser source may be a semiconductor laser. The semiconductor lasers show different characteristics even under the same driving current. Namely, each semiconductor laser has its own light intensity and wavelength. The bar-code reader is designed to operate with a given characteristic of a laser source. Accordingly, the bar-code reader will have trouble if a replacement laser source has a different characteristic.
To solve this problem, the prior art adjusts a drive circuit for driving a replacement laser source so that the laser source may provide a required characteristic. This adjustment must be carried out whenever the laser source is replaced. This is laborious and takes a long time. In addition, it is difficult to precisely adjust the replaced laser source to the required characteristic.
The semiconductor lasers are vulnerable to static electricity. Accordingly, the laser source must be replaced without static electricity. To achieve this, time and labor are needed. Even with careful work, the laser source is sometimes damaged by static electricity.
If the photosensor is incorrectly positioned with respect to the condensing lens, the diameter of a condensed beam will increase. The wide beam is useless to read the thin bars of a bar code. This problem is serious when the bar-code reader is spaced away from the bar codes to be read.
The bar-code reader must be easy and convenient to use.
To recognize bargain merchandise, the operator of the bar-code reader attaches a memo listing the bargain merchandise to a space on a check-out counter. The memo on the check-out counter is usually far from the bar-code reader. Accordingly, the operator must alternately look at the memo and a bar code on merchandise. This is laborious for the operator.
It is important to minimize power consumption and extend the service life of the bar-code reader. For this purpose, the bar-code reader is set in a standby state while it is not reading bar codes. The bar-code reader must automatically be activated before reading bar codes.
To prevent shoplifting, each piece of merchandise is provided with a magnetic tag, which is nullified after the merchandise is paid at the check-out counter. If the merchandise is illegally brought out, a security apparatus at a shop entrance may detect the magnetism of the tag. The bar-code reader and a tag nullification unit are usually separate from each other at the check-out counter, to reduce the working space at the check-out counter.
The bar-code reader is connected to a POS terminal through a cable with or without a connector. The connector may come off the bar-code reader, and the cable may interfere with the operator.
After reading a bar code, the bar-code reader makes a sound to inform the operator of the completion of reading the bar code. To pass the sound, the casing of the bar-code reader has a speaker hole. The speaker hole may guide water into the bar-code reader, to damage the bar-code reader.
A keyboard of the POS terminal is usually placed on top of a tall bar-code reader. The operator must then extend his or her hands to the keyboard. This puts a strain on the operator.